System and method for continuously and simultaneously injecting two or more additives into a main stream of oleaginous liquid

ABSTRACT

Additives are blended with a stream of liquid, for example of diesel fuel, by injecting at least two different additive compositions into the stream, and adjusting the rates of injection and the relative proportions of the injected additive compositions. This enables the consumption of additives to be minimized while enabling desired fuel characteristics to be maintained despite variations in the characteristics of the untreated liquid. The rates of injection may be adjusted by an automatic controller (32) in response to signals from sensors (28, 30) representing characteristics of the liquid before and after treatment.

FIELD OF THE INVENTION

The present invention relates to a system and to a method for blendingadditives with a main stream of a liquid, particularly but notexclusively where the liquid is an oleaginous liquid.

BACKGROUND OF THE INVENTION

Oleaginous materials such as crude oils, lubricating oils, heating oilsand other distillate petroleum fuels, for example diesel fuels, containalkanes that at low temperature tend to precipitate as large crystals ofwax forming a gel structure so that the fuel or oil loses its ability toflow. The lowest temperature at which the crude oil, lubricating oil orfuel oil will still flow is known as the pour point. In the case offuels as the temperature of the fuel falls and approaches the pourpoint, difficulties arise in transporting the fuel through lines andpumps. Further, the wax crystals tend to plug fuel lines, screens andfilters at temperatures above the pour point. These problems are wellrecognized in the art, and various additives have been proposed, many ofwhich are in commercial use, for depressing the pour point of fuel oils.Similarly, other additives have been proposed and are in commercial use,for reducing the size and changing the shape of the wax crystals that doform. Other additives may also retain wax crystals in suspension, andmay be referred to as anti-settling aids. Additives may also be added toimprove other properties of the fuel oil, for example to act ascorrosion inhibitors, or detergents or to inhibit sediment formation.

The invention is relevant but not restricted to fuel oils, includingthose boiling in the gasoline range, but is particularly relevant tothose liquids referred to as middle distillate fuel oils. These fueloils typically boil in the range of about 120° C. to about 500° C., andmay comprise atmospheric distillate or vacuum distillate, or cracked gasoil, or a mixture of straight-run and cracked distillates. The mostcommon petroleum distillate fuel oils are kerosene, jet fuels, dieselfuels, and heating oils. In any event it is almost always necessary toadd a small proportion, for example between 10 and 2,000 ppm by weight,of additives to the liquid as produced by a refinery, in order toproduce a fuel or oil which is suitable for sale and meets desiredspecifications. Typically a refiner would use one additive compositionfor all fuels or might, in some cases, use one additive composition (A)if producing diesel fuel, or a different additive composition (B) ifproducing heating oil; each additive composition (A or B) comprising amixture of the chemically-different types of additive discussed above,chosen to ensure the desired specification is met. Where thecharacteristics of the untreated fuel oil vary (due for example tochanges in refinery operation or changes in crude oil), the refinerensures that the desired specification continues to be met by adjustingthe proportion of the additive composition (say A) which is added. Inthe same way the refiner can produce fuel oils which meet differentspecifications, for example for use in different climates, by adjustingthe proportion of the additive composition (say A) which is added.

SUMMARY OF THE INVENTION

According to the present invention there is provided a system forblending additives with a main stream of liquid, the system comprising aplurality of containers for different additive compositions, means toinject into the main stream of liquid at least two additive compositionsfrom the containers, and means to adjust, during operation, the rates ofinjection and the relative proportions of the different additivecompositions which are injected.

Each additive composition may comprise one or more chemically-differentadditives as discussed above, for example a selection of pour-pointdepressants, wax anti-settling agents, wax crystallization modifiers,corrosion inhibitors etc. and may contain co-additives which improve theeffectiveness of one or other of the additives. These components may bein admixture with a carrier liquid, e.g. dissolved or dispersed in aninactive oleaginous solvent. Some of the additive compositions maycontain a single additive; others may comprise several differentadditives. Preferably the injected additive compositions are injectedsimultaneously, and through a common injector, into the liquid stream.Alternatively they may be injected through different injectors, whichinjectors may be spaced apart either in the direction of the liquid flowor transverse to that direction.

The adjustment means may comprise separate adjustable pumps to pump thedifferent additive compositions to the injector means, or may compriseseparate flow restrictor valves to control the flow rates of thedifferent additive compositions.

Desirably the system is automated, and includes computerised controlmeans to operate the adjustment means in accordance with input datarepresenting measured or measured and computed characteristics of theuntreated liquid or fuel components and input data representing thedesired specification of the blended liquid, and a database relating tothe effect of the different additive compositions on the differentliquids.

By adjusting the relative proportions of the different additivecompositions the overall consumption of additives can be reduced, savingunnecessary expense. This is because the composition of what isinjected, being made up of adjustable proportions of the differentadditive compositions, can be optimised:

a) to accommodate variations in the characteristics of the untreatedliquid, for example due to changes in distillation cut-point, or thetype of crude oil; and

b) to achieve a variety of different product specifications, for exampledifferent fuel grades, or different requirements between summer andwinter, or different product types.

These aims can be achieved while avoiding the waste involved ininjecting a particular additive as part of a standard additivecomposition at higher injection rates than are required in a particularsituation, merely because that injection rate is necessary in relationto another component of that standard additive composition. Inparticular, additive compositions in the present invention may not bediscrete additives optimised for different fuels but sub-assemblies ofadditives that, when admixed in situ, provide the minimum overalladditive consumption.

Desirably, in an automated system, the control means is also responsiveto input data representing measured characteristics of the treatedliquid. The system preferably includes measuring means to determinecharacteristics of the untreated liquid, and of the treated liquid, andto supply the requisite input data to the control means.

In a second a spect the invention provides a method for blendingadditives with a main stream of liquid, the method comprising injectinginto the main stream of liquid a plurality of different additivecompositions, and adjusting, during operation, the rates of injectionand the relative proportions of the different additive compositions toprovide a blended liquid having desired characteristics.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be further and more particularly described by wayof example only and with reference to the accompanying drawing whichshows a diagrammatic view of an additive blending system.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawing, an additive blending system 10 is shown forinjecting additives into a flow of oil/fuel flowing in the directionshown by arrows along a pipe 12 from a production unit (not shown) to astorage tank (not shown). Typically the production unit would be an oilrefinery and the flowing liquid might be intended as heating oil ordiesel fuel. Four containers 14 are arranged near the pipe 12, each withan outlet tube 16 incorporating an electrically adjustable valve 18, allthe tubes 16 communicating via a common manifold 20 to an outflow tube22. The outflow tube 22 incorporates an electric pump 24, andcommunicates with the pipe 12.

A sensor 28 communicates with the pipe 12 upstream of the tube 22, and asensor 30 communicates with the pipe 12 well downstream of the tube 22.The sensors 28, 30 measure characteristics of the oil/fuel in the tube12 before and after the injection of additives, and provide the resultsof these measurements as input data to a computerised controller 32. Forexample the sensor 28 might measure the density, the distillationtemperature, and the cloud point of the oil/fuel, and the sensor 30might measure the cold filter plugging point (CFPP) of the treatedoil/fuel. The controller 32 provides output electrical signals tocontrol operation of the pump 24 and of each of the valves 18.

In use of the system 10 each of the containers 14 contains a differentadditive composition. The controller 32, in response to the input datafrom the sensor 28 and in accordance with the specification of theoil/fuel which is required (this data being provided by an operator tothe controller 32 by means of a keyboard (not shown)), determines whatrate of injection of each of the different additive compositions isrequired. The controller 32 then supplies appropriate signals to thepump 24 and to the valves 18 so that the required quantities of theadditive compositions are injected via the outflow tube 22 into theoil/fuel in the pipe 12. From the input data received from thedownstream sensor 30 the controller 32 can ascertain whether or not thedesired specification is being achieved; and if not, the controller 32can adjust the injection rates of one or more of the additivecompositions accordingly.

The blending system 10 thus operates automatically, blending with theuntreated oil/fuel the necessary combination of additives to provide thedesired specification. It will be appreciated that the operator can atany stage alter the desired specification, for example to change fromproducing winter diesel fuel to summer diesel fuel, and the system 10will automatically make the necessary changes in the additives byselecting a different combination of the additive compositions (ordifferent relative proportions of the additive compositions) from thecontainers 14.

As shown in the drawing the additives are injected into the flowingoil/fuel through the mouth of the outflow tube 22, which thereforeconstitutes the injector. It will be appreciated that the injector maytake a different form, for example a jet eductor as described in WO93/18848. The system 10 is shown as including four containers 14, but itwill be appreciated that it might have a different number, desirablybetween two and eight; the number is merely equal to the number ofdifferent additive compositions which are to be provided. All thecontainers 14 are shown as being the same size, but it may be preferableto store in larger containers those additive compositions of whichlarger quantities are expected to be used. The system 10 mightadditionally be provided with meters (not shown) to measure the volumeof oil/fuel which flows along the pipe 12, and to measure the volumes ofthe different additive compositions which are injected; these meteredvolumes might also be supplied as data to the controller 32, and may berecorded so that operation of the system 10 can be monitored.

The mode of operation of the controller 32 may rely on empiricalcalculations to relate the characteristics of the untreated oil/fuel tothe necessary additions of the additive compositions, or may rely on anexpert system, or a neural network. In any event because the need foradditives may differ considerably for oil/fuels of only slightlydifferent characteristics, and because the characteristics of theuntreated oil/fuel from the production unit may be expected to varycontinuously, it is desirable to monitor the treated oil/fuel and hencemodify the treatment. That is the purpose of the sensor 30. It is alsodesirable to monitor the characteristics of the oil/fuel in the storagetank supplied by the pipe 12, to ensure that it meets thespecifications. It is therefore desirable to provide a further sensorunit (not shown) for this purpose, whose measurements may also besupplied as input data to the controller 32.

A preferred embodiment of the invention has been described above, and itwill be apparent that the system 10 can be modified in a wide variety ofways while remaining with the scope of the invention.

We claim:
 1. A system for blending a plurality of different additivecompositions with a main stream of oleaginous liquid to provide aresulting blended liquid, the system comprising:a plurality ofcontainers for the different additive compositions; common injectionmeans to simultaneously inject into the main stream of oleaginous liquidat least two of the different additive compositions from the containers;means to adjust, during the injection operation, the rates of injectionand the relative proportions of the at least two different additivecompositions which are to be injected; control means to operate theadjustment means in accordance with:input data representing measured ormeasured and computed characteristics of the main stream of oleaginousliquid prior to the injection of the at least two different additivecompositions, input data representing a desired cold filter pluggingpoint specification of the resulting blended liquid, a database relatingto the effect of the different additive compositions, and input datafrom a sensor means for measuring the cold filter plugging point of theblended liquid after injection of the at least two different additivecompositions and for providing signals to the control means representingthe measured cold filter plugging point of the blended liquid as inputdata to the control means.
 2. A system as claimed in claim 1 alsocomprising sensor means for measuring the characteristics of the mainstream of oleaginous liquid prior to the injection of the at least twodifferent additive compositions, and for providing signals representingthose characteristics as input data to the control means.
 3. A methodfor blending additives with a main stream of oleaginous liquid, themethod comprising simultaneously injecting into the main stream ofoleaginous liquid a plurality of different additive compositions from acommon injection means, adjusting, during operation, the rates ofinjection and the relative proportions of the different additivecompositions to provide a blended liquid having a desired cold filterplugging point, and controlling the adjustment step in accordancewith:input data representing measured, or measured and computed,characteristics of the liquid prior to the injection of additives, inputdata representing the desired cold filter plugging point specificationof the blended liquid, signals received from a sensor means measuringthe cold flow plugging point of the blended liquid after injection ofthe plurality of different additive compositions, and a databaserelating to the effect of the different additive compositions.
 4. Amethod as claimed in claim 3 wherein the oleaginous liquid is a fueloil.
 5. A method as claimed in claim 4 wherein the fuel oil is a middledistillate fuel oil.
 6. A system for blending a plurality of differentadditive compositions with a main stream of oleaginous liquids, thesystem comprising:a plurality of containers for the different additivecompositions; common injection means for simultaneously injecting intothe main stream of oleaginous liquid at least two of the differentadditive compositions from the containers to produce a blending liquidcomposition; means to adjust, during the injection operation, the ratesof injection and relative proportions of the at least two differentadditive compositions which are to be injected; control means forproviding output signals to control operation of the means to adjust inaccordance with input data; first input means for providing first inputdata to the control means, said first input data representing one ormore measured, or measured and computed, characteristics of the mainstream of oleaginous liquid prior to injection of the at least twodifferent additive compositions; second input means comprising a sensormeans for measuring the cold flow filter plugging point of the blendedliquid composition after injection of the at least two differentadditive compositions and for providing signals representing themeasured cold filter plugging point of the blended liquid composition assecond input data to the control means, and third input means forproviding third input data to the control means, said third input datarepresenting the desired cold filter plugging point specification of theblended liquid composition.
 7. The system according to claim 6 furthercomprising a database for providing to the control means further inputdata representing characteristics of each of the plurality of differentadditive compositions.
 8. The system according to claim 7, wherein thefirst input means comprises a sensor means for measuring thecharacteristics of the main stream of oleaginous liquid prior to theinjection of the at least two different additive compositions and forproviding signals to the control means representing thosecharacteristics as the first input data.
 9. The system according toclaim 6, wherein the first input means comprises a sensor means formeasuring the characteristics of the main stream of oleaginous liquidprior to the injection of the at least two different additivecompositions and for providing signals to the control means representingthose characteristics as the first input data.
 10. A method for blendinga plurality of different additive compositions with a main stream ofoleaginous liquid to provide a resulting blended liquid compositionhaving a desired cold filter plugging point, the methodcomprising:simultaneously injecting into the main stream of oleaginousliquid at least two different additive compositions; adjusting, duringthe injecting step, the rates of injection and relative proportions ofthe at least two different additive compositions to provide the blendedliquid composition; and controlling the adjusting of the rates ofinjection and relative proportions of the at least two differentadditive compositions in accordance with:(1) first input datarepresenting one or more measured, or measured and computed,characteristics of the main stream of oleaginous liquid; (2) secondinput data comprising signals received from a sensor means for measuringthe cold filter plugging point of the blended liquid composition afterinjection of the at least two different additive compositions andproviding the signals as representative of the measured cold filterplugging point of the blended liquid composition, and (3) third inputdata representing the desired cold filter plugging point specificationof the blended liquid composition.
 11. The method according to claim 10additionally comprising controlling the adjusting in accordance with adatabase providing further input data representing characteristics ofeach of the plurality of different additive compositions.
 12. A methodas claimed in claim 11 wherein the oleaginous liquid is a fuel oil. 13.A method as claimed in claim 12 wherein the fuel oil is a middledistillate fuel oil.
 14. A method as claimed in claim 10 wherein theoleaginous liquid is a fuel oil.
 15. A method as claimed in claim 14wherein the fuel oil is a middle distillate fuel oil.